Field of the Invention
The present invention relates to a solid-state image sensor and a camera equipped with it.
Description of the Related Art
When a high-energy particle enters a solid-state image sensor, a single event latchup (SEL) may occur. The high-energy particle can include, for example, cosmic rays in space and radiation in an atomic power plant or a radiation image diagnosis. The SEL may occur in, for example, a thyristor structure to which pn junctions are connected in series in a CMOS circuit. When the SEL occurs, a voltage line and a ground line are conducted to each other. Thus, an apparatus which takes no measures against this is set in an inoperative state owing to occurrence of the SEL. It is therefore necessary, when the SEL occurs, to restart the supply of a power supply voltage to the apparatus after it is shut off temporarily.
Japanese Patent Laid-Open No. 9-116022 describes a CMOS integrated circuit. The CMOS integrated circuit includes a latchup detection means for detecting occurrence of a latchup and a means for stopping the supply of a power supply voltage to the CMOS integrated circuit in accordance with a signal output from the latchup detection means.
International Publication No. 2002/042797 describes a radiation image diagnosis apparatus. The radiation image diagnosis apparatus includes a plurality of element blocks for detecting radiation, and a plurality of ASICs which correspond to the plurality of element blocks and include processing circuits and readout circuits. When each ASIC receives an abnormal output from the corresponding one of element blocks for some reason, it causes a latchup. The radiation image diagnosis apparatus monitors power supply to each of the plurality of element blocks and stops power supply to the ASIC, out of the plurality of ASICs, which processes a signal from the element block where an abnormality has been detected.
In the radiation image diagnosis apparatus described in International Publication No. 2002/042797, there are a number of pixels which cannot obtain signals due to occurrence of the latchup because the power supply is controlled by using each ASIC, that is, an IC (semiconductor chip) as a unit. Hence, in the radiation image diagnosis apparatus, there are a number of pixels which lose the signals at occurrence of the latchup. Note that International Publication No. 2002/042797 does not suggest that power supply to a partial region in each IC can be controlled.